Hereinafter, a fixed blisk sector is known as a stator guide vanes assembly when it forms part of the compressor of the turbo machine and is known as a nozzle guide vane assembly when it forms part of the turbine of the turbo machine.
A stator guide vanes assembly or nozzle guide vane assembly is formed of angular sectors each comprising a plurality of blades held between two platforms. For example, for an axial-flow turbo machine, the blades are held between a radially outer platform known as the outer platform sector and a radially inner platform known as the inner platform sector.
In one method of manufacturing a blisk, a stator guide vanes assembly sector or nozzle guide vane assembly sector is formed using what is known as the “lost-wax” casting method in which:                first of all a wax (or some equivalent material) model of the stator guide vanes assembly sector is produced;        a mold is created around this model by dipping it into a slurry to form a layer of material in contact with its surface;        the surface of this layer is coated with sand and dried;        this operation of dipping into slurries possibly of different compositions is then repeated to form a shell made up of a plurality of layers;        the wax is then removed from the shell mold, this being an operation whereby the original model is eliminated;        molten metal is poured into the mold and solidifies;        the shell is broken off and manufacture of the stator guide vanes assembly sector is finished off.        
During the manufacture of a stator guide vanes assembly sector using the lost-wax casting method, it is necessary for the platform sectors and the blades to be machined and then polished in order to correct manufacturing defects, and this adds to the cost. In general, it is necessary to use machining to correct the connection between the blades and the platform sectors and this is complicated because of the close proximity of the blades to one another, it being difficult to manipulate the machine tool appropriately.
Aside from the abovementioned disadvantages, a lost-wax casting method is costly to perform because of the numerous stages that the method comprises and because of the equipment needed to implement it.
According to another method of manufacture, the platform sectors and the blades are formed independently of one another and then brazed together. This method, known by those skilled in the art as “mechanically brazed” assembly is a process that is lengthy and complex to perform.
One possible solution might be to use a metal powder injection molding method of manufacture known by the abbreviation MIM, which offers numerous advantages in terms of having mechanical properties that are comparable with the advantages that can be had from forging methods. Furthermore, the cost of series-production of metal components using an MIM method are lower by comparison with a lost-wax casting method.
Remember that a method of manufacturing a metal component using MIM conventionally involves:                preparing a mixture of metal particles and thermoplastic binder;        molding the mixture in a mold to obtain a “green” blank of the component that is to be formed, the blank being of dimensions greater than the final dimensions of the metal component;        removal of the binder from the blank to form what is known as a “brown” blank which is therefore porous, and        sintering the “brown” blank to densify it, which causes shrinkage of the blank, the component thus formed being then at its final dimensions.        
The MIM manufacturing technique is commonly used for the manufacture of relatively small-sized components. Proposals have also been made for this method to be used for the manufacture of the blades and of the platforms independently of one another, as described in published US Patent Application 2007/0102572 A1. The manufacturing method has to be supplemented by an assembly step, preferably using brazing, and this lengthens the manufacturing time.
One solution might be to use the MIM technique to manufacture the blisk sector in a single operation but the MIM method is not suited to the manufacture of large-sized metal components.